Conventional plants for producing plastic curd cheeses from curd obtained by the usual methods comprise:
(a) a curd cutting device into which the curd is loaded in the form of, for example, approximately 20 kg blocks for reduction into fragments or slices;
(b) kneading and plasticising devices comprising screws operating in a tank which is fed both with the curd fragments or slices originating from the curd cutter and with hot water, and mechanical implements in the form of dipping arms or rotary paddles which give the plastic mass delivered by said screws a structure which is fibrous to a greater or lesser extent depending on the type of cheese required;
(c) forming devices which receive the product from the kneading and plasticising machines and divide it into shaped pieces (cylindrical, parallelepiped or spherical) by means of moulds;
(d) hardening devices where the pieces from the forming machines are hardened by being moved countercurrently with circulating water to cool from a temperature of about 50.degree.-65.degree. C.;
(e) salting tanks in which the cooled pieces are placed and are left for a certain time to enable the salt to penetrate into the body of said pieces; and
(f) rooms in which the salted pieces are cured or are packaged.
As stated, the pieces which leave the forming devices have a temperature which varies from 50.degree. to 65.degree. C. depending on the type of cheese to be obtained. In order for these pieces to maintain their shape and to enable the subsequent curing, packaging, storage and dispatch operations to be carried out, their internal temperature must be reduced to 15.degree.-25.degree. C. These pieces are hardened either in or out of moulds depending on their shape and size. Cooling must take place gradually so as not to subject the pieces to thermal shock. This cooling is implemented by placing the pieces in stainless steel tanks generally having a length of from 8 to 20 meters or more, and the pieces are moved countercurrently with a stream of water so that they come initially into contact with water at about 15.degree.-25.degree. C., and then with increasingly colder water which can reach 4.degree. C.
This obviously results in:
a considerable water and energy consumption;
a considerable space requirement;
the need for careful cleaning and sterilising of the tanks which, being uncovered and operating at temperatures which favour bacteria development, represent an environment very favourable to contamination of the pieces, which reduces their life, results in production rejects, and leads to considerable product rejection by the purchaser; and
the need for manual labor in inserting the pieces into moulds (if used), loading the moulds into the tanks, and then extracting the hardened pieces from the moulds.
The subsequent brine treatment which, according to the type of cheese and the size of the pieces can vary from a few hours to some weeks, also requires tanks of considerable length, leading to some of the aforesaid drawbacks of the hardening tanks. Moreover, because of the slowness with which the salt penetration takes place, dairies which produce cheeses in large pieces have to use large rooms (up to 20 m.times.20 m) for the salting operation. To this drawback must be added the fact that the saline solution must be periodically regenerated, requiring further manual labour, the need for vessels used only for this purpose, and considerable energy consumption.